Interrelated and integrated studies of subjects with periodontal diseases are being carried out. The goals of the ongoing studies are to improve knowledge of factors contributing to the etiology and pathogenesis of periodontal diseases, as well as to use this knowledge to monitor the progression of diseases and to improve diagnostic and prognostic capabilities. Subjects are initially screened and clinically characterized by investigators in the Core section of the Center, and appropriate clinical samples and other pertinent information are collected. Clinical, biostatistical, and data management support are provided to the other study groups involved in the Center. During the past year, two categories of subjects have been studied. Subjects with periodontitis are being observed longitudinally to determine clinical, immunological, and bacteriological parameters associated with progressing periodontal sites. Data from these studies will provide information regarding the nature of progression of periodontitis and provide a basis for rationale therapy and prognosis. The second category of subjects are those with early onset forms of periodontitis and their families. Our data indicate that the expression of early onset periodontitis (juvenile periodontitis JP and severe periodontitis SP) is genetically determined. Therefore, we are continuing to enter families identified via probands with these diseases into our studies in order to test genetic hypotheses of the mode of transmission in these diseases and to study clinical and immunological features of these diseases. Finally, in vitro studies aimed at determining some of the immunological pathogenic mechanisms that contribute to periodontal diseases have been accomplished.